Which Replacement Chainring - Now What?
HarryB
my 26/36/48 crank [1]. It's a Shimano 36 tooth, ramped and pinned, 4 bolt
with a BCD of 104mm. Stamped on the chainring is "M9-T36" and on the
crankarm, "FC-M571".
Based on advice I received here, Harris Cyclery, another online store,
and an LBS, I ordered a QBP #CR2770 ring. Well, it turns out that
chainring won't work because the tabs are 1mm too long. Also, the teeth
are not in the same position in relationship to the bolt holes as on the
old one.
So, back to searching the 'net again. I came across a page that lists
Shimano part numbers for this crank [2]. According to that page, the
Shimano Code No. for this chainring is: Y-1DS98200. However, repeated
searches of the 'net fail to show any available in the US, although some
overseas stores might stock them.
Is this M571 such an unusual crankset? It is off my 2003 Cannondale
tandem, but I can't see why the right crankarm and chainrings would be
different than on a single. Am I overlooking something?
[1] http://preview.tinyurl.com/6gv4q4
[2] http://preview.tinyurl.com/5rlxz8
Any additional help would be most appreciated,
Harry
Clive George
news:41H%k.6158$UI2....@bignews6.bellsouth.net...
> Based on advice I received here, Harris Cyclery, another online store,
> and an LBS, I ordered a QBP #CR2770 ring. Well, it turns out that
> chainring won't work because the tabs are 1mm too long. Also, the teeth
> are not in the same position in relationship to the bolt holes as on the
> old one.
Tabs 1mm too long? File them off.
Can't help on your quest to find one which fits out of the box though.
cheers,
clive
cmcanulty
HarryB
Yes, I had thought about that. However, I have two concerns:
1) It seems to me that it is important that all four of the tabs rest
snugly against the raised sections of the spider. Not being a machinist,
I'm not sure that I can do a good job of removing exactly the right
amount of material. Since this is off a tandem and we sometimes carry
quite a bit of gear when we go bike camping, I don't want to risk
shearing the chainring bolts/nuts when we are on tour, miles from an LBS.
Maybe this really shouldn't be a concern because although the small
chainring has tabs, they don't rest against anything - only the 4
chainring bolts hold it in place. Maybe someone can enlighten me about
this.
2) I am sure there is an optimal relationship between the position of the
teeth on this ring and the other ones. Since the teeth on this new ring
are not in the same position as the old ring, I don't want to customize
the chainring in order to get it to fit, only to discover that shifting
has suffered and so can't return it.
Cheers,
Harry
Qui si parla Campagnolo
QBP # CR 2770 is an XT ring and altho both called 104mm BCD, XT
doesn't fit the LX crank you have(thanks shimano). QBP 5812 is what
you need BUT not currently in stock at Quality BUT you need a LX
specific chainring, marked on the package from shimano, NOT an XT.
HarryB
<pe...@vecchios.com> wrote:
>On Dec 9, 8:51 pm, HarryB <Har...@nospam.net> wrote:
>> About a month ago I asked for help in finding a replacement chainring for
>> my 26/36/48 crank [1]. It's a Shimano 36 tooth, ramped and pinned, 4 bolt
>> with a BCD of 104mm. Stamped on the chainring is "M9-T36" and on the
>> crankarm, "FC-M571".
>>
[snip]
>
>QBP # CR 2770 is an XT ring and altho both called 104mm BCD, XT
>doesn't fit the LX crank you have(thanks shimano). QBP 5812 is what
>you need BUT not currently in stock at Quality BUT you need a LX
>specific chainring, marked on the package from shimano, NOT an XT.
I'm confused. I ordered the chainring from bikeman.com and it was in a
sealed package that appears to be from Shimano. Inside is a card, on
the front of which there is a checkmark next to, "Deore LX" and on the
back is a sticker that reads, "FC-M581 Chainring - 36T - Y1FV98010".
On the outside of the package is a bikeman.com sticker that reads,
"CR2770". The chainring itself has stamped on it, "SG-X M9 U-36".
So, Shimano marked the package wrong? It certainly doesn't fit my
crank.
Cheers,
Harry
HarryB
<cmca...@gmail.com> wrote:
>Maybe just as cheap and easier to replace crankset
I have given that some thought. However, this crankset is off a
tandem, so I wish the crankset to look somewhat like the other three
crank arms. So, I would be looking for a black, 26/36/48, Deore
looking, Octalink crankset.
Some casual browsing hasn't brought a slew of candidates to my
attention. But, if I can't find a suitable chainring I may have to
resort to this option.
Cheers,
Harry
bjwe...@gmail.com
> On Wed, 10 Dec 2008 11:35:46 +0000, Clive George wrote:
> > "HarryB" <Har...@nospam.net> wrote in message
> >news:41H%k.6158$UI2....@bignews6.bellsouth.net...
>
> >> Based on advice I received here, Harris Cyclery, another online store,
> >> and an LBS, I ordered a QBP #CR2770 ring. Well, it turns out that
> >> chainring won't work because the tabs are 1mm too long. Also, the teeth
> >> are not in the same position in relationship to the bolt holes as on
> >> the old one.
>
> > Tabs 1mm too long? File them off.
>
> > Can't help on your quest to find one which fits out of the box though.
>
> > cheers,
> > clive
>
> Yes, I had thought about that. However, I have two concerns:
>
> 1) It seems to me that it is important that all four of the tabs rest
> snugly against the raised sections of the spider. Not being a machinist,
> I'm not sure that I can do a good job of removing exactly the right
> amount of material. Since this is off a tandem and we sometimes carry
> quite a bit of gear when we go bike camping, I don't want to risk
> shearing the chainring bolts/nuts when we are on tour, miles from an LBS.
> Maybe this really shouldn't be a concern because although the small
> chainring has tabs, they don't rest against anything - only the 4
> chainring bolts hold it in place. Maybe someone can enlighten me about
> this.
It is not a concern. On most cranksets, if there is a shoulder,
it just locates the center of the chainring at (about) the spindle.
A glance at the shoulder will show that (on all the cranks
I've ever looked at) it cannot exert any force in the direction
of rotation.
You should be using steel chainring bolts, of course.
> 2) I am sure there is an optimal relationship between the position of the
> teeth on this ring and the other ones. Since the teeth on this new ring
> are not in the same position as the old ring, I don't want to customize
> the chainring in order to get it to fit, only to discover that shifting
> has suffered and so can't return it.
You need a chainring. If you can't find the exact fit
one soon, you're going to need this one anyway
so you're not going to return it, even if shifting is a
little bit degraded. Anyway, it doesn't matter that
much what the tooth position is. If the chainring has
the ramps and pins and funny shapes, that helps.
But we shifted for years on flat chainrings and
it worked. If you have STI indexed front shifting
and a triple, a flat chainring is not as good, but
even there there are workarounds (I drilled my own
pins into a flat chainring once). Again the tooth
position is the least of your worries.
Ben
Qui si parla Campagnolo
FC-581 is ala XT, your crank, FC-571 needs the LX chainring...I know
the 581 is an 'LX' but shimano's 104 isn't always '104'.
Qui si parla Campagnolo
ALSO the M581 is 2 piece, Hollowtech II crank where the 571 is
Octalink. WE have seen issues like this before. You need the ring for
the Octalink, LX crank.The bolt diameters are probably the same but
the shelves are placed differently not allowing the chainring you have
to fit. shimano is asking you to upgrade, Methinks
HarryB
<pe...@vecchios.com> wrote:
[snip]
>
>FC-581 is ala XT, your crank, FC-571 needs the LX chainring...I know
>the 581 is an 'LX' but shimano's 104 isn't always '104'.
4 different sources, including Harris Cyclery, told me that QBP's
CR2770 was the correct replacement for this worn chainring. And they
were all wrong even though I had given them the exact number stamped
on the crank arm! A little disconcerting.
I called the (not-so) LBS that told me the CR2770 ring was the correct
one and told them it wasn't. I then gave them the Shimano part number
I found yesterday, Y-1DS98200. They called Shimano and then told me
that they are able to get that ring. So, I ordered it and they should
have it by early next week.
Cheers,
Harry
Qui si parla Campagnolo
Yep, the shimano PDF says the 36t for the M581 is part number
Y-1FV-98010. Let us know if it fits....